Balance
Wolves have tails of many sizes. Same as the cats, wolves use tails for balance. Wolves do not need balance as much as cats because thay cannot climb trees and do not pounce as much.
Speak and Domination
Wolves tails are another way of comunicating. A big part of socializing actually. There are many ways to see what they could be saying. Spotting the Alpha male should be easy. He would be the most broad, and he would have his tail up to simbolize his rank. Am I saying his tail is always up no matter what? No. He will simply raise his tail to show it and put it back down when he feels it got through their head. If they feel that they are being challenged, threatened, or just don't like another wolf they will attack. If the alpha looses he is no longer alpha, the winner is. They will Dominate.